Explosive stud having ogival point and reduced dimension tip projecting therefrom



Oct.

EXPLOSIVE] DIM ENSION TI THEIR Filed March 18, 1954 R. J. M DONALD 2,768,552 STUD HAVI OGIVAL POINT AND REDUCED ROJECTING EFROM INVENTOR. ROBERT J. MacDO/VALO ATTORNEYS United States Patent EXPLOSIVE STUD HAVING OGIVAL POINT AND REDUCED DIMENSION TIP PROJECTING THEREFROM Robert J. MacDonald, Columbus, Ohio, assignor, by mesne assignments, to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware Application March 18, 1954, Serial No. 417,188

Claims. (Cl. 85-30) This invention relates to fastening devices or studs adapted to be driven into such refractory materials as concrete and steel by the combustion of a charge of propellent powder, and more particularly to a stud adapted to be secured in steel plate of a thickness comparable with the diameter of the stud.

The conventional design of a stud adapted to be explosively secured, as shown in the patent to Catlin et al., No. 2,663,259, comprises an ogival point of a length of about twice the stud shank diameter. In use, a stud of this type penetrates the host material, for example, structural steel, to a depth about equal to the length of its ogival point, and if the steel plate receiving the stud is of lesser thickness the stud undesirably protrudes from the back side of the plate. If the propelling force is so reduced as to materially reduce penetration, holding power is diminished to practically nothing.

The present invention contemplates a stud so designed that it is capable of being secured to and into steel plate of a thickness comparable with the stud diameter without protruding from or breaking the continuity of the back side of the plate.

In the drawings:

Fig. 1 is a fragmentary side elevation of a typical stud embodying the present invention.

Fig. 2 is a fragmentary side elevation of a modified stud embodying the present invention.

Fig. 3 is a fragmentary side elevation of a stud embodying a further modification within the present invention.

Fig. 4 is a sectional elevation of a stud according to the present invention as driven into a steel plate of a thickness comparable with the diameter of the stud.

The invention comprises a particular configuration of the metal-penetrating portion of the stud. Whereas the conventional stud comprises a relatively long ogival point, adapted for deep penetration into the receiving material, the studs of this invention comprise a comparatively short and more sharply curved ogival point section and, extending therefrom in alignment with the stud shank 13, a small diameter ogival or conical tip 11. The surface of tip 11 is merged with that of the point 10 through the curved or inclined intermediate section or surface 12. The tip 11 is an essential feature; in its absence, a stud having the blunt ogival point just described merely indents and rebounds from the surface of host metal, instead of penetrating and bonding. The tip initiates the shearing of the host metal necessary for stud penetration, as well as initiating the outward flow of the host surface, with its film of seizure obstructing oxides and other foreign matter. The penetration facilitating tip also promotes the straining of the host metal (14, Fig. 4) throughout its thickness, and the accompanying formation on the back side of the host of the bulge 15. Such straining of the host throughout its thickness has been found essential to good bonding. In its absence, the elastic spring-back of the host partially or completely breaks the bond between stud and host.

2,768,552 Patented Oct. 30, 1956 It is important that the surface 12 intermediate the base of the conical or ogival tip 11 and the ogival point 10 be inclined outwardly away from the tip. A flat shoulder resists penetration and obstructs the outward flow of surface impurities. Except for the absence of flats, that is shoulders substantially perpendicular to the stud axis, the configuration of the intermediate surface i2 is not critical, and a variety of shapes are shown in Figs. 1, 2 and 3, respectively.

The bond between host metal and stud closely resembles a weld and the presence of martensite in the better bonded stud surfaces indicates transient temperatures aoove transformation, the heat being derived from. excessive friction between the relatively moving surfaces of the stud and the host. The maximum seizing is on the portion of point 14) adjacent the intermediate surface 12, the seizing gradually diminishing outwardly and rearwardly. There is scattered seizing on the surface of tip 11, and a lesser amount at the intermediate surface 12.. Seizing is greatly facilitated by polishing the stud surface, say to a fineness of not over 33 micro inches as measured on a profilometer. Fine polishing increases holding power. Stainless steel, as well as carbon steel, is excellent stud material.

A typical stud as illustrated in the drawing has a shank diameter of about 0.25. The length of the tip 11 is about 0.05, and the base diameter of the tip is about 0.10". The tip may be either ogival, as shown in Fig. 1, or conical, as shown in Fig. 3. The length of intermediate section 12 is about 0.0125", and the length of point 10 is about 0.0875". A stud of these dimensions and proportions driven into A" structural steel plate, as illustrated in Fig. 4, has an average holding power of 5,100 pounds.

Similarly, a A stud with the modified ogival point 10 and intermediate section 12, as shown in Fig. 2, in A structural steel plate, has an average holding power of 5,200 pounds.

The stud of Fig. 3 is substantially similar to that of Fig. 1, except that the tip 11 is conical rather than ogival. A A1 stud of this type, driven into A" structural steel plate, in the manner illustrated in Fig. 4, has an average holding power of 5,250 pounds.

If the tip 11 and point 10 are merged in a single ogival point of the same overall length, the holding power is greatly diminished, being about 3,300 pounds.

If such a point is made conical, the holding power is further diminished.

While a stud of Mt shank diameter has been described in detail, substantially the same proportions are applicable to studs of other sizes. In general, the radius of curvature of the ogival point 10 is comparable with the radius of the shank 13. While it may exceed shank radius by a small amount, it does not approach shank diameter. The length of said point 10, exclusive of the intermediate surface 12, should not exceed the radius of the shank and is preferably about six-tenths of such radius. To avoid piercing the back side of a sheet of host metal of a thickness comparable with stud diameter, the length of tip 11 should be not over half and preferably about four-tenths the shank radius. The diameter of the base of the tip, where its surface merges with that of the intermediate section .12, is not greater and preferably somewhat less than the radius of the shank, say about eight-tenths thereof. As above stated, the configuration and dimensions of the intermediate section 12 are not critical, provided only this section slopes outwardly away from the base of the tip and does not comprise a flat shoulder.

What is claimed is:

1. A stud adapted to be explosively driven into a metal plate of a thickness comparable with the diameter of the stud without perforating the back surface of the plate, said stud comprising a substantially cylindrical shank, an ogival point of curvature on a radius not substantially greater than the radius of the stud shank, and a centrally disposed tip projecting from said point in alignment with said shank; the surfaces of said tip and said point being joined in an abrupt rearwardly sloping surface of transition, the length of said tip being not more than one-half the radius of the shank, the volume of said tip being at least as great as that of a right circular cone having a length and base diameter respectively equal to the length and maximum diameter of said tip.

2. A stud according to claim 1, in which said tip is of conical configuration.

3. A stud according to claim 1, in which said joining surface is of curving configuration.

4. A stud adapted to be explosively driven into bonding relation in a metal plate of a thickness comparable With the diameter of the stud without perforating the back surface of the plate, said stud comprising a substantially cylindrical shank, an ogival point of curva- 4 ture on a radius not substantially greater than the radius of the stud shank, and a centrally disposed ogival tip projecting from said point in'alignment with said shank and having a maximum diameter not greater than the radius of said shank, the length of said tip being no greater than one-half the radius of said shank, the surfaces of said tip and said point being joined in an abrupt rearwardly sloping surface of transition.

5. A stud according to claim 4, in which the surfaces of said point and said tip are polished to a fineness of not over 33 micro inches.

References Cited in the file of this patent UNITED STATES PATENTS 541,280 Johnson June 18, 1895 893,963 Wheeler July 21, 1908 2,549,993 Temple Apr. 24, 1951 2,663,259 Catlin Dec. 22, 1953 FOREIGN PATENTS 612,041 Germany Apr. 12, 1935 

